The present invention relates to a method for making a metal seal for flanged joints, particularly for high-vacuum applications. The invention further relates to a metal seal made by said method.
It is known from German design patent No. 17 62 330 to fabricate metal seal rings for flanged joints from sheet aluminum. This is done by punching circular rings from the aluminum sheet and then upsetting the inner rim of the ring for formation of a sealing bead. A drawback of this prior-art method is that in the case of large seal cross sections, and particularly of those which deviate from circularity, the attendant technical complexity renders it uneconomical.
To overcome this drawback, it has already been proposed to provide flanged joints for use in radioactive, toxic or explosive environments, and also for high-vacuum applications, with seals made of aluminum wire. Wire of superpure aluminum of a diameter ranging from 1 to 3 mm is preferably used. Such wire is supplied on reels. To make a seal, the desired length of wire is unreeled, given the shape of the desired seal, and welded together.
The mounting of such seals is complicated especially when the flange faces to be sealed are disposed vertically. In the past, these seals were secured in place in the mounting position with adhesive tape. Then a silicone adhesive was applied in a few spots, and when it had set the adhesive tape could be removed. This mounting technique has the further drawback that wetting of the seal with silicone adhesive on the medium side or on the sealing-face side cannot be avoided even when the utmost care is taken. Since various working media, for example, uranium hexafluoride, spontaneously react with this adhesive, the risk of leakage is high. In many applications, this mounting technique therefore cannot be employed.